Implantable biosensors for monitoring health have witnessed rapid developments in the past decade. While innovations in microelectronics enabled continuous miniaturization of sensing devices, battery technology became a limiting factor. For this reason research in energy harvesting systems has increased drastically. Today the leading energy harvesting technologies are piezoelectric, thermoelectric, electromagnetic movement, biocatalytic fuel cells, photovoltaic, radio frequency. It is desirable to improve the efficiency of energy harvesting properties of these implantable biosensors or implantable devices.